SALICYLIC ACID-MEDIATED ALLEVIATION OF CADMIUM TOXICITY IN BASMATI RICE (Oryza sativa L.)

Abstract

The Cd accumulation might result disturbances in plant metabolism causing several physio-biochemical and structural changes ultimately declining the crop productivity. Having recognized the adverse effects of Cd on plants it is imperative to understand the mechanisms of Cd effects through its accumulation, transportation and the relationships of Cd effects with growth, antioxidant systems and the mineral nutrients, and then the contribution of SA in alleviating the Cd toxicity in basmati rice. The experiments were conducted in two phases (plant and callus) under different combinations of Cd (control, 100, 500, 1000 and 1500 μM) without or with SA (0.0 and 0.1 mM) with four genotypes of basmati rice (Basmati-198, Basmati-2000, Basmati-370 and Kashmir Basmati). The results revealed variable Cd accumulation pattern in the both culture systems (seedling and callus). Roots showed higher Cd accumulation as compared to shoot and callus. The lower Cd accumulation of callus than root exhibited less sensitivity of callus to Cd-induced stress. A two phase linear concentration-dependent Cd accumulation pattern was observed in root and shoot whereas in callus Cd accumulated in a linear concentration-dependent fashion with the elevating Cd levels in the both culture media. However, protective effect of SA on root or shoot and the callus inhibited the Cd accumulation from the both media revealing the possibility of occurrence of the formation of stable SA-Cd complexes. Higher amounts of H 2 O 2 and MDA caused Cd-induced oxidative stress elevating the activities of antioxidants (CAT and POD) which accelerated the accumulation of solutes disturbing mineral nutrients and water status in the both media. The uneven SOD activity exhibited that differences existed among the genotypes to withstand the Cd toxicity. The application of SA in combination with the elevating Cd stress showed improvements in the SOD activity indicating that higher SOD activity might modulate the activities of other enzymes and regulate the solutes maintaining water relations under Cd-induced oxidative stress and ultimately the growth in the both culture media. Based on Cd translocation factor and the root STI, and the callus BCF and STI factors, Basmati-198 showed more tolerance to Cd toxicity followed by Basmati-2000 and Basmati-370 whereas Kashmir Basmati was observed prone to Cd toxicity.